I added backticks to your post, so the code appears as code. I also made the topic title more descriptive.

As for your question: use nocom to disable translation and use noreorient to disable rotation. The following outputs the geometry in Bohr correctly. (If you want Angstroms, mutliply by qcel.constants.bohr2angstroms.) Does this answer your question?

Yes, it is my question.
But I also have the last question. Why do not you design “nocom” and “noreorient” as the methods of the geometry class. Just use follow ways to disable translation and rotation:
geom = “”"
C -1.86708863 0.79113923 0.00000000
H -1.51043420 -0.21767077 0.00000000
H -1.51041579 1.29553742 0.87365150
H -1.51041579 1.29553742 -0.87365150
H -2.93708863 0.79115241 0.00000000
“”"

mol = psi4.geometry(geom)
mol.nocom()
mol.noreorient()

Maybe I think it is more convenient. Just in my opinion.

Another question, where can I find the “qcel.constants.bohr2angstroms”?

The problem is that the center of mass is changed and the molecule reoriented during initialization, before you have a chance to call nocom or noreorient.

qcel.constants.bohr2angstroms is in the 1.3 release of Psi4. This release is about a week old and is fully stable. You can get it here. If you don’t want to use Psi4 1.3, the conversion factor has a different name. I need to know what version you’re using to find the name of the conversion factor there.

I don’t know if Psi’s orientation is the same as Gaussian’s, but right, we move the molecule into a standard orientation. That way, the center of mass is at the origin and the symmetry elements are along the x, y, z axes. That makes things easier for the program.

That is the correct link to download 1.2.1. In 1.2.1, the conversion factor is 0.52917720859. You should be fine just typing psi4.constants.bohr2angstroms in 1.2.